After IC chips are formed on a semiconductor wafer (hereinafter, referred to as “wafer”), a probe test is performed on the wafer by using a probe apparatus in order to inspect electrical characteristics of the IC chips. The following is a brief description of an inspection flow of the wafer in this probe apparatus. First of all, a wafer is unloaded by a transfer mechanism from a carrier where a plurality of wafers are accommodated. Next, a position alignment process called as a pre-alignment process and a process for acquiring an ID or the like formed on the wafer which is called as an OCR process are performed on the wafer. Thereafter, the wafer is loaded into a probe apparatus main body, and then is mounted on a wafer chuck capable of moving in X, Y and Z directions and rotating about a Z axis. Next, electrode pads formed on the wafer and probes of a probe card provided above the wafer chuck are imaged by an upper camera provided above the probe apparatus main body to face the wafer chuck and a lower camera provided at the wafer chuck, respectively. Then, a fine alignment process for precisely aligning the positions of the electrode pads and the probes is performed. Thereafter, in a state where the probes, e.g., probe needles, are brought into contact with the electrode pads of the IC chips of the wafer, electrical signals are transmitted from the probe needles to the electrode pads, thereby inspecting electrical characteristics of the IC chips.
The inspection of the electrical characteristics includes several processes and thus requires a long period of time. Thus, in order to increase a throughput, it is preferable to minimize waiting time of the probe apparatus main body (during which the inspection is not performed). To be specific, the transfer mechanism is provided with a loading arm for transferring a wafer to be inspected from the carrier and into the probe apparatus main body and an unloading arm for returning an inspected wafer from the probe apparatus main body to the carrier, the loading and the unloading arm being movable independently. During the wafer inspection, a wafer to be inspected is taken out from the carrier, and the pre-alignment process or the OCR process is performed in advance on the corresponding wafer. After the inspected wafer is unloaded from the probe apparatus main body, the wafer to be inspected is immediately loaded into the probe apparatus main body. Accordingly, it is possible to reduce the waiting time of the probe apparatus main body which is required in exchanging wafers.
In this probe apparatus, in order to reduce a foot space, a plurality of, e.g., two, probe apparatus main bodies are provided at a common transfer mechanism, and wafers are transferred by the common transfer mechanism to and from the probe main body apparatuses. The following is a specific description of an exemplary case where wafer inspections are individually performed in the two probe apparatus main bodies. For example, a single wafer is unloaded from the carrier, and the pre-alignment process and the OCR process are performed on this wafer. Next, the wafer is exchanged with an inspected wafer in, e.g., one probe apparatus main body, and the inspected wafer is returned to the carrier. Thereafter, a wafer to be inspected is unloaded from the carrier, and the pre-alignment process and the OCR process are performed on this wafer. This wafer is exchanged with an inspected wafer in, e.g., the other probe apparatus main body. In this probe apparatus configured as described above, the wafers are transferred by the common transfer mechanism to and from the two probe apparatus main bodies, so that a foot space occupied by one transfer mechanism can be reduced. As a result, the foot space of the probe apparatus can also be reduced.
However, after a wafer in one probe apparatus main body is exchanged, a long period of time is required until a wafer in the other probe apparatus main body is exchanged, because there arises a need to access to the carrier and perform the pre-alignment process or the OCR process. Therefore, when a wafer in one probe apparatus main body is being exchanged after the inspection, if the inspection of a wafer in the other probe apparatus main body has also been completed, the other probe apparatus main body waits for a long period of time until a wafer in the other probe apparatus main body is exchanged, which deteriorates the throughput.
Meanwhile, there is known a method in which the loading and the unloading arm are provided with separate driving units so that they can move independently. In this method, a loading/unloading of a wafer to/from the carrier and a loading/unloading of a wafer to/from the probe apparatus main bodies are carried out by different arms. To be specific, a wafer is unloaded from the carrier by the unloading arm, and the wafer is transferred from the unloading arm to the loading arm. Next, the wafer is loaded into the probe apparatus main body by the loading arm. Therefore, while the loading arm accesses to a probe apparatus main body, the unloading arm can take out a next wafer from the carrier. Accordingly, the transfer time of the wafer decreases and, further, the waiting time of the probe apparatus main body decreases. However, in this configuration, the loading and the unloading arm are provided with separate driving units as described above, so that a cost of the probe apparatus increases and, also, an operation sequence of the arms becomes complicated.
Although a substrate transfer unit having a plurality of arms is disclosed in Japanese Patent Laid-open Publication No. 2001-250767, a specific operation sequence of the arms or the like in the probe apparatus is not described at all.
In order to perform the fine alignment, there arises a need to ensure a movement region of the wafer chuck in the probe apparatus main body. However, as the wafer is scaled up, the movement region is expanded, so that the apparatus is scaled up. Further, the expansion of the movement region of the wafer chuck increases movement time and alignment time. Meanwhile, a demand for an improvement of throughput leads to a development of a loader unit capable of loading a plurality of carriers or a common loader unit shaped by a plurality of inspection units. However, there is a trade-off relationship between a high throughput and a large occupation area of the apparatus.
As for a conventional probe apparatus aimed to provide a high throughput, there is known an apparatus described in Japanese Patent Laid-open Publication No. H6-66465. In this apparatus, two inspection units including a wafer chuck, a probe card and the like are connected to both sides of a loader unit. Since, however, the inspection units are not designed to be scaled down, the inspection units installed at both sides of the loader unit increase the occupation area of the apparatus. Further, the wafer transfer deteriorates due to the presence of a pincette for transferring a wafer from/to a carrier loaded into the loader unit and two swing arms for transferring the wafer between the pincette and the two inspection units, the pincette being movable in a longitudinal direction of the loader unit. Moreover, the moving paths of the swing arms need to be ensured, so that the apparatus cannot be scaled down.